Coronary Heart Disease and TMLR--Coronary Heart disease is prevalent in modern society, wherein the reduced blood supply to the heart, due to blockages in one or more of the coronary arteries, is the most common cause of heart attacks and death from heart disease. Currently, surgical intervention using coronary artery bypass graft surgery and/or coronary balloon angioplasty is the most common procedure to treat this condition.
Recently, procedures for modifying a human heart to imitate the blood delivery method of a lizard heart is currently being used as an alternative or adjunct to both coronary artery bypass graft surgery and coronary balloon angioplasty. Normally, a person can only undergo coronary bypass surgery twice, since the risks will begin to outweigh the benefits after that point. Thus, in the past, a patient who has already had two coronary bypass surgeries was left with no recourse. Others patients have failed repeated coronary balloon angioplasties, and many persons are not suitable candidates for coronary bypass surgery or coronary balloon angioplasty. These persons likewise are left with no treatment options.
Early attempts to create direct blood supply to the myocardium of mammals, known as transmyocardial revascularization (TMR), consisted of producing tiny channels in mammalian and human hearts with needles or pre-heated wires. These methods met with limited success since, although the channels closed by clotting at the outside surface of the heart due to exposure to air, and did allow for some internal blood delivery, the channels soon healed over entirely and failed to continue to enhance the blood supply. Early attempts were also made to graft a blood vessel from the aorta directly into the heart muscle to provide an internal source of blood. While some benefits were seen, the surgery was technically demanding and the procedure was eclipsed by the introduction of coronary artery bypass graft surgery.
To overcome these problems, Mahmood Mirhoseini and Mary M. Cayton attempted transmyocardial revascularization using a pulsed CO.sub.2 laser to make the channels. This procedure has come to be known as transmyocardial laser revascularization (TMLR). Mirhoseini M., Cayton M. M., "Revascularization of the Heart by Laser" J Microsurg 2:253, June, 1981. The laser forms each channel by vaporizing a passageway completely through the wall of the heart. The relatively clean channel formed by the laser energy prevents the channel from healing over, and the channel either closes by clotting at the heart's outer surface, due to exposure to air, or manual pressure can be applied until bleeding from the channel ceases. In some cases, a suture is required to close the channel. However, if bleeding cannot be stopped, or if bleeding resumes at a later time, after the patient is no longer in surgery, the patient may require emergency surgery or may die.
While most, if not all of the laser created channels close over time, the reduction in angina pain achieved by TMLR increases over a period of six months and is stable for at least an additional six months. In animal studies, it was found that extensive angiogenesis was seen in the area surrounding the channels, which is belied to be the main reason for TMLR's increasing benefit over six months and further extended benefit.
Since the body stores only small amounts of angiogenic growth factors in the heart, it is obvious that supplementing the body's supply of natural (endogenous) growth factors with growth factors produced by recombinant technology or to infect the myocardium with genes able to cause myocardial cells to express the growth factors, could yield greater angiogenesis and thus greater therapeutic benefits.
Angiogenesis and Atherosclerosis--Angiogenesis is the fundamental process by which mammalian systems form new blood vessels in normal growth and in response to injury. Normal angiogenesis is tightly regulated, and uncontrolled angiogenesis has been implicated in many disease states, including cancer. Specific angiogenic growth factors and other substances have been identified in the art, such as vascular endothelial growth factor or VEGF, fibroblast growth factor or FGF, and angiopoetin. (See for example Folkman and Shing, 1992, J. Biochemistry 267(16):10931-10934; Thomas, 1996, J. Biochemistry 271(2):603-606).
Initial work in the area of angiogenesis revolved around the discovery and characterization of angiogenic agents. For example, Abraham, J, et al ("Nucleotide Sequence of a Bovine Clone Encoding the Angiogenic Protein, Basic Fibroblast Growth Factor" Science, Vol. 233, 545-548, 1986) taught the nucleotide sequence of acidic FGF (aFGF), and the structures of acidic FGF (aFGF or FGF-I) and basic FGF (bFGF).
Recently it has been shown that the administration of purified human FGF-I was able to induce neoangiogenesis in ischemic myocardium, after injection concurrent with internal mammary artery (IMA)/left anterior descending coronary artery (LAD) anastomosis surgery. Schumacher, B et al., "Induction of Neoangiogenesis in Ischemic Myocardium by Human Growth Factors" Circulation, 97: 645-650 (1998).
Gene Therapy--With the identification and characterization of various angiogenic agents, it was possible to purse direct molecular intervention in vivo of the processes of neovascularization. Gene therapy has been a long desired goal of biomedical science, but effective introduction of genes causing the expression of VEGF or FGF into cells of the myocardium takes lengthy exposure which is not practical in a beating heart. Inserting an angiogenic gene into the genome of a replication deficient virus, which retains its ability to infect cells, was proposed to overcome this problem. Berlener, K L ("Development of adenovirus vectors for the expression of heterologous genes" Biotechniques 6:616-629, 1988) was one of the earliest reports on the use of such viruses for gene transfer.
Work in the art of gene expression vectors and delivery has advanced greatly in the last few years. For example, Ziverbel, J A, et al., ("High-level recombinant gene expression in rabbit endothelial cells transduced by retroviral vectors," Science, 243: 220-222, 1989) demonstrated the practical use of retroviral vectors to carry genes into endothelial cells. However, prior and subsequent work has shown that the use of retrovirus vectors is problematic, as complete and permanent deactivation of the retrovirus cannot be assured. Stratford-Perricaudet, L D, ("Evaluation of the transfer and expression in mice of an enzyme-encoding gene using a human adenovirus vector" Hum. Gene Ther. 1:241-256, 1990) was also an early report of human adenovirus gene therapy work. Methods for delivery of gene therapy to specific targets has met with substantial progress, however specific technical issues still require further work (see Mulligan, R C, "The Basic Science of Gene Therapy", Science, 260: 926-932 (1993), for review).
Continued research on gene therapy and angiogenic factors have yielded information about coordinated action of various factors, for example, Suri, C et al. ("Increased Vascularization in Mice Overexpressing Angiopoetin-1" Science, Vol. 282, 468-471, October 1998), showed that angiopoetin-1 is necessary to mature and maintain new vessels initially created by introduction of VEGF or aFGF. This work demonstrates that additional substances, such as angiopoietin-1, can be used to maintain the integrity of the newly created vessels for a long term effect.
Continued research involving treating blood vessels to either enhance or inhibit angiogenesis related to atherosclerosis using gene therapy has yielded useful results. For example, Feldman et al., "Percutaneous Adenovirus-mediated Gene Delivery to Normal and Atherosclerotic Arteries In Vivo: a Comparative Study" Circulation 90(4), part 2:I-517, Abstract #2783, 1994), and Pastore, Christopher et al., "Intraluminal Delivery of Pluronic Gel Enhances Adenovirus-Mediated Arterial Gene Transfer: a Morphometric Study" Circulation 90(4), part 2:I-517, Abstract #2782, 1994), illustrates use of viral vectors to treat blood vessels by direct administration after denuding the blood vessel wall. Schulick, Andrew et al., "A Therapeutic Window for In Vivo Adenoviral-Mediated Gene Transfer" Circulation 90(4), part 2:I-516, Abstract #2778, 1994), illustrate various viral concentrations beyond which efficiency is not increased, using a rat carotid artery system. Other in vitro experiments also demonstrate systems for evaluating viral expression vectors, for example Pili, Roberto et al., ("Angiogenesis Induced by Adenovirus-mediated Gene Transfer of Secreted and Non-Secreted Forms of Acidic Fibroblast Growth Factor" Circulation 90(4), part 2:I-516, Abstract #2777, 1994), demonstrated the use of aFGF encoding viral vectors to induce angiogenesis from cultured human umbilical vein endothelial cells. Blazing, M A et al., ("A New Adenoviral Vector With Enhanced Expression Characteristics" J. Invest. Med. 43 Supplement: 278A, 1995), examined viral transfection using a cultured vascular smooth muscle cell system. Wang, Mary et al., ("Replication Defective Adenovirus Enables Transduction By Retroviral Vectors of Cells Outside Their Host Range" J. Cellular Biochem. Supplement 18A, Abstract DZ100, page 222, 1994), found a 2 to 4 fold increase in infectiveness over unmodified vector. Armentano, D., et al., ("Second Generation Adenovirus Vectors for Cystic Fibrosis Gene Therapy" J. Cellular Biochem. Supplement 18A, Abstract DZ102, page 222, 1994) describe another improved viral vector.
Ischemic heart disease has also been identified as an attractive potential target for gene therapy intervention. As discussed by Williams, R S, ("Southwestern Internal Medicine Conference: Prospects for Gene Therapy of Ischemic Heart Disease", Am. J. Med. Sciences, 306(2): 126-136 (1993)), a number of pathophysiologic features or manifestations of ischemic heart disease present attractive targets for direct gene therapy, including atherosclerosis, cell proliferation, angina, and thrombosis.
Coronary Heart Disease, Angiogenesis and Infision--With greater understanding about angiogenic factors and genes expressing the same, collectively "angiogenic agents", and their potential to induce neovascularization, infusion of such angiogenic agents into one or more coronary arteries has been described to attempt increased blood supply to the heart. However, an undesirable side-effect of this route of administration is that virus is released into the general circulation.
The use of angiogenic agents and their potential for treating heart disease were discussed by Marsha F. Goldsmith ("Tomorrow's Gene Therapy Suggests Plenteous, Potent Cardiac Vessels", JAMA Vol. 268, No. 23, Pg. 3285-3286, 1992) in Medical News & Perspectives column. In this article, she discusses work by Jeffrey Leiden & Elian Barr (U. of Chicago), including naked DNA injection into cardiac and skeletal muscle and the use of an adenovirus (replication sequences deleted) vector containing an angiogenic gene which was injected into a coronary artery, infecting the entire artery.
Leclerc, G, et al., "Percutaneous Arterial Gene Transfer in a Rabbit Model", J. Clin. Invest., 90: 936-944 (1992), describe approximately 50% transfection efficiency for delivering foreign DNA to balloon-injured arteries using a DNA-liposome transfection vector.
Further work by Barr, E, et al. ("Efficient catheter-mediated gene transfer into the heart using replication-defective adenovirus", Gene Therapy 1:51-58, 1994), showed that five days after infusion administration the virus was detected in the brain, lungs, liver, kidneys and testes. This was after a single infusion into a coronary artery at 2.times.10.sup.9 -1.times.10.sup.10 p.f.u. of adenovirus-linked gene. Thus, infusion of adenovirus-linked genes into a coronary artery resulted in the undesirable result of disseminating the angiogenic capable genes systemically, which could enable an occult tumor to grow by extending its blood vessel system.
Angiogenesis, the Heart, and Direct Injection--Attempts to directly inject angiogenic agents directly into the muscle of the heart, while attractive, have had various technical difficulties that reduces overall efficacy of gene therapy. When the therapeutic agents, in a liquid medium, are injected into the wall of a beating heart, on the next compression of the heart, much of the liquid is expelled by contraction of the muscle.
Lin, H., et al. ("Expression of recombinant genes in myocardium after direct injection of DNA" Circulation 82: 2217-2222, 1990), showed the feasibility of gene transfer into the cells of the myocardium by direct injection of naked DNA. However, later papers showed much higher cell penetration rates and transformation efficacy with genes incorporated into the genome of replication defective adenovirus or other viral vectors.
Giordano, F J et al., ("Reduced Myocardial Ischemia After Recombinant Adenovirus Mediated In-Vivo Fibroblast Growth Factor-5 Gene Transfer" J. Invest. Med. 43 Supplement: 278A, 1995), demonstrated successful infection of myocardial cells from an intracoronary injection of replication deficient viral vector encoding FGF-5.
Studies of the specific transformation of heart muscle cells was greatly advanced by the work of Barr, E and Leiden, ("Systemic delivery of recombinant proteins by genetically modified myoblasts" Science 254:1507-1509, 1991) who demonstrated that skeletal muscle cells of a host could be genetically modified and injected into the myocardium. This was useful since myocytes cannot be cultured in-vitro. However, it was found that injection of these cells into cardiac muscle, resulted in an inflammatory response and fibrous formations.
Barr, E, et al. ("Induction of angiogeneses following in-vivo gene transfer into myocardium" Circulation Vol. 84, No. 4, Supplement II, Pg. II-430, 1991) described the use of pRSV-FGF5 plasmid containing the FGF-5 gene injected into left ventricular wall of rats. The results showed that resulting capillary density was 32% higher than in control animals who were injected with the viral plasmid alone.
Stratford-Perricaudet, L D, et al. ("Widespread long-term gene transfer the mouse skeletal muscles and heart" J. Clin. Invest. 1992; 90:626-630) which examined lasting effects of gene transfer into such tissues.
French, Brent et al., "Feasibility and Limitations of Direct In Vivo Gene Transfer into Porcine Myocardium Using Replication-Deficient Adenoviral Vectors" Circulation 90(4), part 2:I-517, Abstract #2785, 1994), observed a much higher efficiency of transformation (140,000 times higher) using a viral vector versus "naked" DNA plasmid. The infiltration of transformation using the viral vector injection rarely showed up more than 5 mm from the injection site.
Similarly, angiogenic genes/viral vectors were shown to be more efficient in infecting myocardial cells than genes in a liposome delivery system.
Losordo, D W, et al., "Gene Therapy for Myocardial Angiogenesis", Circulation, 98: 2800-2804 (1998), describes initial clinical results with direct myocardial injection of phVEGF.sub.165 as sole therapy for myocardial ischemia in men who had failed conventional therapy, and suffered from angina. Naked plasmid DNA encoding for VEGF was injected directly into the ischemic myocardium (anterolateral left ventricular free wall) via a mini left anterior thoracotomy (125 .mu.g in 4 aliquots of 2.0 mL each). After about 60 days post-operation, the patients appeared to benefit from the treatment.
Several U.S. patents are related to gene therapy, viral vectors, and in particular angiogenic agents, including U.S. Pat. No. 5,849,997 (Grosveld et al.); U.S. Pat. No. 5,849,718 (Grosveld); U.S. Pat. No. 5,849,572 (Glorioso et al.); U.S. Pat. No. 5,846,947 (Behr et al.); U.S. Pat. No. 5,661,133 (Leiden et al.); U.S. Pat. No. 5,837,511 (Crystal et al.); U.S. Pat. No. 5,792,453 (Hammond et al.); U.S. Pat. No. 5,328,470 (Nabel et al.); U.S. Pat. No. 5,698,531 (Nabel et al.); U.S. Pat. No. 5,707,969 (Nabel et al.); U.S. Pat. No. 5,840,059 (March et al.,); U.S. Pat. No. 5,389,096 (Aita et al.,); and U.S. Pat. No. 5,554,152 (Aita et al.).
While a growth factor, a gene coding for a growth factor, or such a gene incorporated in a vector may be injected into an arrested heart with a simple syringe, much of the angiogenic agent would be expelled on the next contraction of a beating heart. As a result, creating a space within the heart muscle, in which the angiogenic therapeutic could repose for sufficient time for its absorption would be desirable.
TMLR and Angiogenic Agent Therapy--TMLR procedures using an adenovirus vector encoding human Profilin was not found to be effective in stimulating additional angiogenesis in a study reported by Fleischer, K J et al., ("One-month histologic response of transmyocardial laser channels with molecular intervention" Ann Thorac. Surg. 62(4): 101-8, 1996). The procedure appeared to create more inflammation in the tissues by stimulating release of VEGF but no additional angiogenesis.
Recently, Sayeed-Shah, V, et al. ("Complete Reversal of Ischemic Wall Motion Abnormalities by Combined Use of Gene Therapy With Transmyocardial Laser Revascularization" J. Thorac. Cardiovasc. Surg. 116(5): 763-9, 1998; and 1998 abstract), describe the injection of VEGF genes along with TMLR. The results indicate that they were able to normalize heart wall motion in animals in which a coronary artery was artificially constricted, a result superior to injection of the same gene or TMLR alone.
The prior art also uses several mirrors mounted on an articulating arm to reflect carbon dioxide laser energy toward the tissue to be vaporized. Maintaining the proper alignment of these mirrors at all times, however, is difficult and positioning the arm is inconvenient for the operator. Laser energy transmitted through optical fibers could eliminate this problem and avoid making a large opening into the patient's chest in order to perform the TMLR procedure.
Further, the use of lasers whose energy can be transmitted through optical fibers, such as argon-ion, have also been proposed for performing TMLR through a percutaneously inserted catheter from the inside of the heart chamber, Lee G. et al., "Effects of Laser Irradiation Delivered by Flexible Fiberoptic System on the Left Ventricular internal Myocardium," Am Heart J., September, 1983.
However, if argon-ion laser energy is applied to make the channel completely through the heart wall, since such lasers are of significantly less power than the CO.sub.2 laser used in TMLR, the optical fiber must be present in the heart wall for a longer period of time than diastole, when the heart's electrical activity is minimal and the heart is momentarily at rest. If the procedure cannot be completed during diastole, within approximately 0.6 seconds (at a heart rate of 60 beats per minute), between heartbeats when the heart's electrical activity is minimal, a life threatening arrhythmia may result, and mechanical damage to the heart muscle during its compression may occur.
Using a typical TMLR procedure and device, if the gene therapy agent in a liquid medium is injected into the channel in the wall of a beating heart, the next contraction of the heart muscle will force much of the agent out of the channel. Generally, it is desired that the channels be made primarily within the heart's myocardium and the inner portion of the endocardium since the myocardium and endocardium have a greater need of an alternative supply of blood than the heart's outer surface (epicardium).
The methods and apparatus of the present invention avoid the problems of the art methods of administration of angiogenic agent by creating a space or pocket within the heart muscle using a laser, which does not extend completely through the endocardium into the heart chamber, with minimal interruption of the epicardium, if the space is created from the epicardial surface of the heart, or into the epicardium or outer surface of the heart, with minimal interruption of the endocardium, if the pocket is created from the endocardial surface of the heart chamber, into which an angiogenic agent may be injected and trapped, avoiding its dissemination into the circulation.
Since the pulsed laser energy of a wavelength highly absorbed by water (CO.sub.2 or Holmium:YAG, for example) or protein (Excimer, for example) causes an acoustic shock and pressure wave in the tissue, causing endogenous (naturally occurring) growth factors to be released that likewise cause neovasculorigation, a complementary angiogenic effect can be achieved.
If using an optical fiber, whose distal end is encased in a short length of double-beveled syringe needle of 18 gauge or smaller, the entry of the needle (without laser energy emission) into the heart wall creates a cut, rather than a puncture, which almost immediately seals and remains closed.